The present invention relates to a temperature control capable of always keeping an object at a fixed temperature.
A typical example of a prior art temperature control involves employment of bimetal material whereby a mechanical contact is opened or closed to control the supply of power to a heater. It is also well known to use a temperature sensor such as a thermister or a positive temperature characteristic thermistor to keep an object at a desired temperature.
These prior art temperature controls generally comprise a heating element adapted to heat an object and a temperature sensor (for example, a bimetal and a thermistor) adapted to the supply of power to the heating element. A feed-back loop including the temperature sensor controls the supply of power to the heating element and keeps the object at a given temperature. Nevertheless, it is difficult to accurately maintain the object at the desired temperature because substantial heat resistance is present while heat from the heating element is transmitted to the object. A temperature increase or decrease in the object and even temperature detection will be time-delayed due to the heat capacity of a heat transmission medium and the object, and the heat resistance of the heat transmission medium. This makes a control system unstable and the gain of the control system relatively lower.